Dr. Jeff Hersh: Mosquitoes transmit chikungunya virus

Monday

Jul 21, 2014 at 3:22 PMJul 21, 2014 at 3:22 PM

By Dr. Jeff HershMore Content Now

Q: I heard there is a new viral disease from Africa that has just come to the Americas. What is this?A: It sounds like you are referring to the chikungunya virus.Chikungunya (which means “stooped walk” in a Tanzanian language; named because the joint pain from it makes people walk in a bent-over fashion) is a viral illness transmitted by infected mosquitoes (only certain types of mosquitoes can carry this virus). The cycle of infection is: a mosquito bites a person (or certain animals) carrying the virus. The virus then multiplies inside the mosquito before making its way to their salivary glands where it may then be passed on to another person (or animal) when they bite to feed again. In some cases, chikungunya can be transmitted from mom to fetus, or even via a blood transfusion; these modes of transmission are, thankfully, rare.Chikungunya has been endemic in parts of Africa for a long time. With so many world travelers, it is not surprising that this virus was eventually carried by infected people to the Americas; several hundred thousand suspected cases have been diagnosed in Central and South America over the last couple of years. Some U.S. travelers have been infected abroad and then diagnosed on their return to the states; although I am unaware of any cases transmitted from infected mosquitoes within the U.S., the types of mosquitoes that can carry this virus do exist here, so it is likely just a matter of time until there are cases of chikungunya acquired within the U.S. borders.It is thought that most people infected with chikungunya develop symptoms within two days to two weeks after the virus is transmitted from the bite of an infected mosquito, although some studies after outbreaks in Africa have shown that up to 50 percent of people who were infected — as demonstrated by antibodies to the virus in their blood tests — did not report any symptoms. The most common symptoms are fever (sometimes as high as 104 degrees Fahrenheit or more) and joint pain/swelling (arthralgia/arthritis, symmetrical in up to three quarters of cases). Multiple joints are usually affected, with the hands and ankles being the most common, but any joint (including joints in the spine, legs, arms, etc.) may be involved. The joint pain can be severe enough to become disabling, hence the name of the disease. Other common symptoms may include rashes (in over half of all patients), headache, muscle aches, gastrointestinal symptoms and swollen glands.The acute flare-up of symptoms typically lasts a week or two, but for many patients symptoms may persist; over three quarters have joint symptoms (ranging from to joint stiffness in the morning to more severe joint pain/swelling to other symptoms) persist for over a month, and 50 percent for 6 months or longer. Most patients with persistent symptoms also develop cryoglobulinemia, the presence of abnormal proteins that thicken in cold temperatures and which may cause inflammation and/or damage to blood vessels.Severe symptoms (even death) may rarely occur as a complication of chikungunya and may include breathing compromise, heart inflammation or failure, liver or kidney failure, eye inflammation/conditions and/or neurological symptoms.Chikungunya is diagnosed based on the symptoms and risk factors (primarily being in an area where it is endemic); however, other diseases, such as dengue fever, may have similar symptoms (and indeed dengue fever may be transmitted by the same types of mosquitoes and in the same geographic areas as chikungunya), so definitive diagnosis may be challenging. There are specialized blood tests that can be obtained (as clinically indicated) to confirm the diagnosis. These specialized tests are usually utilized to confirm the specific diagnosis when there is a localized outbreak of disease.There are no specific treatments for chikungunya, so supportive therapies to treat pain, inflammation or other symptoms using non-steroidal anti-inflammatory medications (NSAIDs), other pain medications, steroids or other treatments are utilized as needed.Although after someone is infected with chikungunya, they seem to develop lifelong immunity (so they cannot get infected a second time), at this time there is no vaccination to prevent a first infection. Therefore, prevention revolves around avoiding mosquito bites by using effective insect repellent (such as products containing high concentrations of DEET), having screens or using air conditioning (or even mosquito nets) while sleeping, and wearing long pants and long sleeves.—— Jeff Hersh, Ph.D., M.D., can be reached at DrHersh@juno.com.